9.1.2 Epithelium of Digestive Tract: An Impenetrable Barrier Against Microbial Invasion

The gastrointestinal tract (GIT) is covered by mucous membrane, which protects the GIT against microbial invasion by means of its various kinds of secretions.

Definition

Epithelium of Digestive Tract: The gastrointestinal tract (GIT) is covered by mucous membrane, which protects the GIT against microbial invasion by means of its various kinds of secretions.

Main Idea

• The gastrointestinal tract (GIT) is covered by mucous membrane.
• The mucous membrane protects the GIT against microbial invasion.
• It does so by means of its various kinds of secretions.
• Hydrochloric acid in the stomach is secreted by oxyntic or parietal cells.
• Hydrochloric acid kills the bacteria present in food.
• Various digestive enzymes present in gastric juice, intestinal juice and pancreatic juice also digest the bacteria present in food.

Core Concept

• **GIT** = gastrointestinal tract
• Mucous membrane = covers the GIT
• Protection = against microbial invasion
• Hydrochloric acid = secreted by oxyntic or parietal cells
• Hydrochloric acid = kills bacteria present in food
• Digestive enzymes = in gastric juice, intestinal juice, pancreatic juice
• Digestive enzymes = digest bacteria present in food

Detailed Explanation

Epithelium of Digestive Tract: An Impenetrable Barrier Against Microbial Invasion

• The gastrointestinal tract (GIT), is covered by mucous membrane, which protects the GIT against microbial invasion by means of its various kind of secretions.
• Hydrochloric acid in the stomach is secreted by oxyntic or parietal cells that kills the bacteria present in food.
• In addition, various digestive enzymes present in gastric juice, intestinal juice and pancreatic juice also digest the bacteria present in food.

Summary Table of Digestive Tract Defences

Intermediate Level

Epithelium of Digestive Tract

Sources of Defences

Summary of Digestive Tract Defences

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. GIT is covered by mucous membrane.
• 2. Mucous membrane protects against microbial invasion.
• 3. Protection is by secretions.
• 4. Hydrochloric acid is secreted by oxyntic or parietal cells.
• 5. Hydrochloric acid kills bacteria in food.
• 6. Digestive enzymes are present in gastric juice.
• 7. Digestive enzymes are present in intestinal juice.
• 8. Digestive enzymes are present in pancreatic juice.
• 9. Digestive enzymes digest bacteria in food.
• 10. The GIT is an impenetrable barrier against microbial invasion.

Remember

• - **GIT** = gastrointestinal tract
• - Mucous membrane = covers the GIT
• - Protection = against microbial invasion
• - Hydrochloric acid = secreted by oxyntic or parietal cells
• - Hydrochloric acid = kills bacteria present in food
• - Digestive enzymes = in gastric juice, intestinal juice, pancreatic juice
• - Digestive enzymes = digest bacteria present in food

Common Mistakes

• 1. Forgetting the role of mucous membrane — Covers the GIT.
• 2. Mixing up the source of hydrochloric acid — Oxyntic or parietal cells.
• 3. Forgetting the role of digestive enzymes — Digest bacteria in food.
• 4. Mixing up the juices — Gastric juice, intestinal juice, pancreatic juice.
• 5. Believing the GIT is not important — It is an impenetrable barrier.
• 6. Mixing up the defences — Mucous membrane, hydrochloric acid, digestive enzymes.
• 7. Thinking hydrochloric acid only digests food — It also kills bacteria.
• 8. Forgetting the role of the stomach — Site of hydrochloric acid secretion.
• 9. Mixing up the types of cells — Oxyntic or parietal cells.
• 10. Thinking the GIT is sterile — The GIT has defences against microbes.

Quick Revision

The gastrointestinal tract (GIT), is covered by mucous membrane, which protects the GIT against microbial invasion by means of its various kind of secretions. Hydrochloric acid in the stomach is secreted by oxyntic or parietal cells that kills the bacteria present in food. In addition, various digestive enzymes present in gastric juice, intestinal juice and pancreatic juice also digest the bacteria present in food.

60-Second Revision

• GIT = gastrointestinal tract
• Mucous membrane = covers the GIT
• Protection = against microbial invasion
• Hydrochloric acid = secreted by oxyntic or parietal cells
• Hydrochloric acid = kills bacteria present in food
• Digestive enzymes = in gastric juice, intestinal juice, pancreatic juice
• Digestive enzymes = digest bacteria present in food
• Warning: Hydrochloric acid kills bacteria; digestive enzymes digest bacteria

NEXT TOPIC

• Chapter:
• 9. Immunity

• Topic:
• 9.1.3 EPITHELIUM OF RESPIRATORY TRACT: AN IMPENETRABLE BARRIER AGAINST MICROBIAL INVASION

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